Retirement benefits will see a slew of changes in 2012: Seniors will get significantly bigger Social Security checks and face only modest increases in Medicare premiums. Workers will also be eligible to defer taxes on more money in their 401(k) plans and get more disclosures about the fees and expenses they are paying. Other changes on the horizon? Rising Social Security taxes, slightly better Medicare Part D gap coverage, more 401(k) match reinstatements, and increased IRA income limits.